diff --git a/deps/v8/tools/testrunner/testproc/progress.py b/deps/v8/tools/testrunner/testproc/progress.py
index 9e13504aba6415..1699e6c17bf438 100644
--- a/deps/v8/tools/testrunner/testproc/progress.py
+++ b/deps/v8/tools/testrunner/testproc/progress.py
@@ -365,7 +365,7 @@ def __init__(self, junitout, junittestsuite):
 
     self.outputter = junit_output.JUnitTestOutput(junittestsuite)
     if junitout:
-      self.outfile = open(junitout, "w")
+      self.outfile = open(junitout, "wb")
     else:
       self.outfile = sys.stdout